Lens.



W. CHURCHILL.

LENS.

APPLICATION FILED PEB. 3,1910.

Patented July 30, 1912.

UNETED ESTATEg ra rnrrr WILLIAM GHURCHILL, OF CORNING, NEW YORK, ASSIGNOR T0 CORNING GLASS WORKS, OF CORNING, NEW YORK, A QORPORATION OF NEW YORK.

LENS.

Specification of Letters Eatent.

Patented Jul 3 ildffi.

Application filed February S, 1910. Serial No. 541,836.

To all whom it may concern:

Be it known that I, WILLIAM CHURCHILL, a citizen of the United States of America, and a resident of Corning, county of Steuben, State of New York, have invented certain new and useful Improvements in Lenses, of which the following is a specification.

Certain disadvantages are present in the semaphore lens now in common use with a smooth outer convex face and a corrugated or stepped inner face. Among these disadvantage. are the loss of light falling on the miters and projected thereby out of the edges of the lens at such an angle with the axis thereof as to render them useless for the purpose for which such lenses are used.

My invention has for its object to avoid these and other defects of the previous 'constr cti on and for this purpose I employ what may be termed an inverted semaphore lens, that is one having a smooth convex rear face and a corrugated or stopped outer face, and further combine therewith a cover glass, which not only projects the corrugations of the outer face from the accumulation therein of dirt, snow, etc, but which may be so shaped as to possess optical properties.

My improved lens will be fully described in connection with the annexed drawings in which 4 Figure 1 is a sectional view through a lens constructed in accordance with this invention. Fig. 2 is a corresponding view of a11- oiher form in which a meniscus cover glass is used.

The element A of the lens has a convexed rear face 13, B, B etc, and a front face composed of a series of zones CU, C C C -C united by initcrs CC, C -C etc, and is surrounded by a flange D, by which it may be held in a suitable casing". With such. an element when properly placed in front of a sturcc of illumination E, while there will be produced certain dark bands coinciding with the positions of the miters such bands do not indicate a loss of light, as is the rase with the llSlllll smooth face semaphore, this being due to the fact that the niiters are located substantially in the path inwhich the rays from the source after refraction in the rear face. pass atthe several miters through the element and hence practically none of the rays falling thereon are lost. This is illustrated by following the course of any ray E B which falls upon the rear face of the lens at a proper point to be refracted therethrough in the line TE -C adjacent to the miter. It :will be noted thatthe line of passage 'B B through the element is parallel with the face of the miter so that any ray falling upon the lens closer to the principal axis than the points B will after passing through the element fall upon the zone (P C and not upon the miter itself. this inverted lens in that it is not possible, due to the constructional demands, to place the initers when employed on the rear face of the lens in such planes as will not intercept the impinging rays, whereas with the inverted lens this may be easily done and. in fact done to advantage as fa. as construc tion is concerned. Moreover the dark bands so produced by the initers are less in width with the ii'iverted lens than with the usual semaphore.

In connection with railway or semaphore lenses it must be further remembered that it is not desirable to produce an absolutely parallel beam but on the contrary that one of gradually increasing diameter or spread demanded. Among the advantages of the inverted lens herc described is that it reduces the actual focal distance from the cenler of the lens to the flame thereby .ii'ii'ording an increased an'iount of such spread, over and above that obtainable with the present form of semaphore lenses in which, as the lens projects out from the lamp casing t.

istance from the center of th', lens to the flame is relatively great, being of the inch lens wit a inch focus nearly inches. This lty cannotmercly ()YGTCUDIO by i the smooth face semaphore lens been in l'llti't case the loss of light upon the niitei s much increased and at the same time the spherical aberration becomes much greater, whichwhile, o coma. not as objectionable in railway lens as in tlmse intended for optical work. is detrimental and which can be practically eliminated by the lens of the inverted type. It will be noted that the inverted lens here described has no projection of the lens beyond the case and hence the liability of the damage or ln-ealnige is much reduced.

To protect the Zones and miters upon the outer face of the inverted lens both from This is an important advantage In.

injury and from the accumulation of foreign matter thereon a cover glass F may be placed upon the fGIV/illi'l face thereof, This glass a plain, concave-convex or may he a meniscus (as shown in Fig. 2), forming With the element A a douldet. By preference such glass cover is provided with a flange F of the same diameter as the flange D. of the element- A so that it may be contained "Within theeaine mounting and may he so shaped as to fit snugly upon the out zone C G of such element.

Having thus described my invention what I claim and desire to secure by Letters Patent is 1, A lens having a smooth curved refracting rear face and a stepped front face consisting of zones united by miters the miters being located substantially parallel to the path of the rays passing through the lens Where such miter-s are located.

2. A lens having a smooth curved refracting coinrex rear face and a stepped front from face consisting of zones united by miters, and a meniscus element located in front thereof, substantially as described.

f. A lens having a smooth convex refracting rear face and a stepped front face eohsisting of zones united by niiters in combination with a cover glass of concave-convex form located upon the forward face of thelens and fitting and resting upon the outer of said zones.

5. A lens having a smooth convex ref 'act ing rear face and a stepped front face consisting of zones united by initers located substantially parallel to the path of the rays passing through the lens Where such Initers are located in combination with a cover glas of concavo-convex form located upon the forward face of the lens.

6. A lens having a smooth convex refracting rear face and a stepped front face con sisting of Zones united by miters located substantially parallel to the path of the rays passing through the lens where such miter-s are located in combination with a cover glass in the form of a meniscus element located in the front thereof and forming With the main lens a doublet.

NHJLlAh/f CHURCHILL.

Witnesses Manon 'WHn'LooK, E. H. CURTIS. 

